Why does Once Human drop FPS when loading base components?

Building a complex survival base, whenever large components loaded, the FPS would plummet from 110 to 40 without warning, which was maddening. I first tried changing the PCIe mode from Auto to Gen4 in BIOS, but the drops persisted and I even got occasional black screens. I used the GamePP BIOS Load-Line Voltage Adjustment Wizard to tune VDDQ voltage from 1.1V to 1.15V and optimized the Load-Line control mode. Cinebench R23 showed 2 hours of zero errors, while HWiNFO showed VRM temps at 55-62℃ and GamePP tracked fans at 1400-1600RPM.